Attached is Grails application which uses Drools. It works with Drools 6.0.0.Beta5, but stops with CR1. You need Grails on your PC to run the application. Easiest is to use http://gvmtool.net/ to install Grails 2.2.4. * unpack grails-drools6.tar.gz * cd to this folder * run: grails run-app * visit http://localhost:8080/grails-drools6/drools/index * this time you will see "ok" in browser, because it will use 6.0.0.Beta5 * stop grails by pressing Ctrl+C now to reproduce the problem: * comment out line 2 in grails-drools6/grails-app/conf/BuildConfig.groovy * run: grails run-app * visit http://localhost:8080/grails-drools6/drools/index * this will fail with message related to compiling of "global com.xtmotion.builder.DroolsFactBuilder kb;" in xtrules.drl